


The Third Of A Pair

by ReaderInserted



Category: Ao no Exorcist | Blue Exorcist
Genre: Aged-Up Character(s), Don't Like Don't Read, F/M, I Might Be To Shy For That, I Might Not Write Smut, M/M, Manga & Anime, OT4, Separate Childhoods, Slow Burn, Spoilers, The Baal Aren’t Actually Blood Related Canon, Triplets, college aged
Language: English
Status: In-Progress
Published: 2020-11-17
Updated: 2020-11-16
Packaged: 2021-03-09 02:47:10
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 1,812
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27057442
Author URL: https://archiveofourown.org/users/ReaderInserted/pseuds/ReaderInserted
Summary: When they were all born, Rin was the only one glowing in Satan’s flame. Shiro and Mephisto did not expect (y/n) to have inherited the blue flames.She lights up for the first time, when she’s six, channeling her demonic awakening.Mephisto keeps the small hell spawn contained in his mansion while she goes through her awakening.Eventually being moved completely in with Mephisto.She does eventually get to see Yukio during cram school though it’s not the same.For Thirteen years, she’s been told that she’s the only sibling who inherited the satanic fire. Oh, how upset she is when she finds out everyone close to her has been lying to her for all of those years.
Relationships: Amaimon (Ao no Exorcist)/Reader, Amaimon/Okumura Rin/Mephisto Pheles, Amaimon/Okumura Rin/Mephisto Pheles/Original Character(s), Mephisto Pheles/Reader, Okumura Rin/Reader
Comments: 1
Kudos: 11





	1. Chapter 1

**Author's Note:**

> PSA:
> 
> So this story contains Anime and Manga spoilers. 
> 
> As of Friday, October, 17th, I still haven't finished the manga... actually I've only read up to book 12... yeah I got some catching up to do, but I'm poor and I'm doing the best I can. I don't like reading the manga digitally, I like supporting the creater. So some of the info may only be Anime canon and not Manga canon but trust me as I catch up I will tailor this to fit the manga more appropriately. 
> 
> I’ll update this note every time I get to read the next book In line. I always buy three at a time, but it could be months apart cause gotta save up for ''luxury'' items. Thank you for reading this psa, enjoy the story.

**Summary for the Chapter:**

> This isn’t really a story yet. I’m still working on it but the draft was about to be deleted so I needed to do something

This isn’t really a story yet. I’m still working on it but the draft was about to be deleted so I needed to do something


	2. Third Degree Burns

**Notes for the Chapter:**

> *This is the full story summary it’s kind of important that you read it or you might be confused with the first chapter*
> 
> When they were all born, Rin was the only one glowing in Satan’s flame. Shiro and Mephisto did not expect (y/n) to have inherited the blue flames.
> 
> She lights up for the first time, when she’s six, channeling her demonic awakening. 
> 
> Not having a plan for this situation, the two men cannot save face before the Grigori find out about the little spawn.
> 
> Infront of everyone, she showed signs of calming and listening to the flamboyant demon king. Because of Mephisto being able to pacify her, It’s decided by the Grigori that (y/n) (if she can be trained to help them) has potential, and she’s granted the opportunity to prove herself useful to the order when she’s older. 
> 
> Mephisto keeps the small hell spawn contained in his mansion while she goes through her awakening. Mephisto kept her under control and mostly harmless. (Y/n) had injured no one. Except Mephisto’s house furnishings.
> 
> After she calms down (Y/n) learns she is going to live with Mephisto permanently. That means she must grow up without her brothers.
> 
> She does eventually get to see Yukio during cram school and when they train together with Shiro. Though it’s not the same.
> 
> For Thirteen years, she’s been told that she’s the only sibling who inherited the satanic fire. Oh, how upset she is when she finds out everyone close to her has been lying to her for all of those years.

Pacing back and forth, decorative metal chains clank against her shoes. The red plush carpet of the limo absorbs her hastened footfalls. Unfamiliar music danced through the space, gracing her ears, but doing nothing to calm her nerves.

There's a nervous fluttering in her stomach. In response to the feeling she chewed on her thumbnail. The sharp keratin resisted breaking, teeth biting but causing no damage to the naturally dark claw.

Devilish emerald eyes lit with mirth. Amused with the dual haired girl. He studies her with leisure, leaned back against cushiony leather seats as she works herself into an enthusiastic frenzy.

Despite the gut wrenching news of Shiro’s death a few days prior, excitement now pumped through her veins, gripping her tight. She couldn’t sit still, needing to expunge this energy, she paced. It’s not helping. Each minute that drags by is causing her giddiness to kick up another notch.

The minutes are crawling past her, scraping by, grating her nerves like nails on a chalkboard. It’s agony to wait. 

Before this, she could write letters to her older brother, but they strictly prohibited her from having any other form of contact with him, thanks Grigori. To reduce a pair of siblings to pen pals is cruel. Even for them. Now, her brother is a borderline stranger.

They only send messages to each other once a week, they have their own lives to tend too. Though looking into the mail, to see a letter from Rin, would always brighten whatever mood she was in. His letters were highlight of her her week. 

Yukio got to see her regularly. If Rin had known that, he’d have demanded to see her too. There used to be too many reasons that that couldn’t happen. Plus, the Gregori had their conversations monitored, to “make sure she admitted nothing to the eldest triplet.”

Now, Rin gets to be a part of her life. She can’t wait. With a bounce in her step, her mind is racing with ideas. What’s Rin like in person? She knows he’s funny, his letters are proof enough of that. Is he introverted or extroverted? He says he’s a loner, but does he have any people skills? In a letter, you can have any personality you want. He's a complete mystery to her.

She wonders how adult Rin looks. (Y/n)’s memories of their youth together are so blurred. Is he taller than her? Shorter? Do they resemble each other? She and Yukio don’t. Not with half of her hair being snow white, and the other dark blue. No one allowed her to receive photos from him, and she couldn't send him photos.

Shiro had fought tooth and nail to keep Rin away from this world of demons. Consequently, Shiro died in the process.To say it devastated her when Shiro died is an understatement. (Y/n) wasn’t told the specifics of how Shiro passed or how Rin got his temptaint. She’s assumes he got injured by what every killed her mentor. At most (y/n) is allowed to go on the trip to retrieve Rin.

The warm sunlight, that’s pouring into the limousines stretched out windows, gets drowned out once they passed under a bridge. Temporary shadows dance across the pair, causing (y/n)’s movements to resemble a slow-moving praxinoscope.

Her paces stop and she freezes in place. Her thoughts come to a screeching halt, heart speed picking up... this is the first time she's gotten to leave True Cross since her trial with the Grigori. The first time she’s trusted enough to leave. Too thrilled with the news that she would get to meet her big brother for the first time, since they were little kids, that the rest of the information escaped her.

(Y/n)’s mind is far off at the moment, the fast reflexes engrained into her muddled by her mind’s wandering, she doesn’t react fast enough when the car jolts, launching her forward. She doesn’t brace for any impact before she’s crashing into Mephisto.

In a flash, Mephisto is in front of (y/n) wrapping her into an embrace to keep her in place. His grip bruising around (y/n)’s waist. (Y/n) stumbles with her feet for a moment before she straightened. She glances at the man.

Shade shrouding half of his face. Her brilliant cyan eyes can see his Cheshire grin, obvious in the light. His piercing emerald orbs, glowing in the shadows.

(Y/n)’s fists had bunched up the smooth fabric of Mephisto’s shirt when she fell. Vanilla and Cherries engulf and comfort her. Mephisto’s scent. She could sense her pupils elongate. She had to break eye contact; her face hot.

Mephisto growls out an amused hum. (Y/n) can feel his chest rumble with the sound. Fingers lifting her chin, Mephisto encourages her to turn her attention to him with a gentle movement. She’s not aware she leans into his touch.

“Your reflexes are as astute as ever, darling.” His grin blooms into a full on smile, his fangs on full display. Teasing the girl.

(Y/n) growled and flashed her fangs in response to the demon.With a shove , she pushes him and backs away. Her face burns.

She released a huff and crossed her arms across her chest. With a glance over her shoulder and a quirked eyebrow, she asks, “why’d the limo stop?”

Brilliant green yes focused on adjusting the purple glove that adorns his wrist, feigning disinterest, “We’ve arrived at the humble little monastery your brothers' call ‘home’.” Mephisto side eyes (y/n) to gauge her reaction, he’s not disappointed.

Unknowingly imitating an excited puppy, her head whips around and she runs over to ogle out the window. Sprawling herself over the red leather seats cushions in an controlled tumble.

Her flushed face cooled against the smooth glass as her bright blue eyes dart around, soaking in the surroundings outside. There are buildings everywhere, granted there’s less than at True Cross Town, and they’re a lot more spaced out here. She can see actual patches of grass and flowers, not artificial ones! 

A chuckle came from behind her and she pouts, much more aware of her childish behavior all of a sudden. Sparing a few more moments, she looks for the monastery, though she can’t find it.

Eyes rolling, she pushes herself back up, standing. She straightens out her outfit and brushes off imaginary dust from her shoulder. Peering up, she meets Mephisto’s gaze, there’s a grin plastered on his face. (Y/n) grit her teeth. Clearly, the demon found her ecstatic reaction humorous. With a cough to clear her throat, she crosses her arms and widens her stance, self-conscious. Huffing, “Where’s the monastery?”

“Oh,” Mephisto’s eyebrows shoot up, eyes widening in mock recollection. He points his finger in the general direction. “Well, it’s around the block and down the street.” The gleam in his eyes suggests he’s enjoying every second of this. 

(Y/n) squints are eyes and glares. “Well then Mepphy, I would say we haven’t exactly ‘arrived’ then; have we?”

A crack resounded through the limo when he clapped his hands together, causing (y/n) to jump back. The movement didn’t go unnoticed. “Very astute of you to point out (Y/n), good job! Your quite right, we haven’t arrived yet.” the smile slipped from his face, suddenly serious. “We need to discuss something first.”

With a tilt of her head (Y/n) arches an inquiring brow. “Discuss…?”

“Well, many things, of course, but mostly these simple things. One: You are going to help guide Rin while he trains to be an exorcist at the cram school. Essentially, you’ll be going through cram school training again.”

What? Her heart plummeted. Is she going to have to start over from the very beginning? Is she going to lose all of the sprogress she’s made over the last Thirteen years? 

A gasp escaped the blue-eyed girl, her arms dropped to her sides as she took a shocked step forwards. “WHAT? But Mepphy I just gr—”

A finger clad in purple leather shot out and silenced her. To say the least, that action annoyed her.

With her nerves having been frayed at all day, she didn’t think before she was nipping at the offending appendage with a snarl, flashing her fangs in a challenge. 

Mephisto’s eyes grew dark and his pupils contacted, smirk growing on his face, he raised his hands up in a surrendering gesture and backed away, continuing.

“Two: Do not flame up or talk to Rin about the demonic heritage you both share.”

Nodding, “Okay, now that one makes sense. But I can’t lie to him forever. He’s going to have to learn, eventually.”

“All will be revealed in due time dear (y/n).”

“Well, that sure answers my question. Doesn’t it?” shaking her head, “Okay, what else.”

“That’s it.”

The dual haired girl stares into ember eyes, trying to find a lie. With scepticism laced in her voice, she asks, “Really, that’s it?” 

Mephisto nods his affirmation. Whistling, already bored with the conversation. 

“Then why did we have to stop? Why couldn’t you have just told me all of that on the way here?”

“Because you most likely would have forgotten it with how excited you were.”

Not waiting for the girl to reply Mephisto walks past (y/n) and knocks on the wall separating them from the driver. The car begins moving again. 

About to pass the girl again, she stops him, tugging on his cape. Face once againg hot, she doesn’t make eye contact when he turns to look at her. Instead focusing her gaze on the fluffy carpet that graces the floor. “Does this mean I'm going to lose all the progress I’ve made with my training?” 

It takes the demon a moment before it clicks and chortle of mirth bubbles from his chest. Leaning over he places a hand on his knee. Wiping a faux tear from his eye, he says, “Oh God no (y/n).” mirth coated every word.

“It just means your going to be baby sitting Rin in class, I’ve seen the boys report cards before he dropped out of high school and his grades were pitiful. He’s going to need the help now since this is college. And before you ask yes, you'll be baby sitting him in regular classes and cram school. No this doesn’t effect your individual progress.”

“Oh.”

“Do you feel better now?”

“Much, Thank You.”

“Always a pleasure,” Mephisto placed himself in front of the limo door, ready to make an amazing entrance, or exit. Depending in the way she looks at it. “now brace your self this time before the limo stops.”

**Notes for the Chapter:**

> Like I said not finished yet
> 
> Oh also for the sake of this story the birth of the triplets will follow the second half of season one. Because I'm more familiar with it and it fits this better.
> 
> I don't know much about the birth in the manga but what I do know about it I just can't make it fit. I'm sorry if that bothers you please have an open mind, thank you.


End file.
